The present invention relates to a processing method of a thermally developable photosensitive material which exhibits excellent size repetition accuracy and specifically, to a thermally developable printing plate-making photosensitive material which is suitable for color printing.
Conventionally, in the printing and plate-making field, solution waste generated along with the wet process for image forming materials has caused problems regarding worakability, and in recent years, a decrease in the processing solution waste has been strongly demanded in terms of environmental protection and room saving.
Thus, a technique for light heat photographic material for a technical photographic use is demanded in which exposure can be sufficiently carried out using a laser image setter, and sharp and bright images with high resolving power can be achieved.
As such techniques, methods are well known which are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,487,075 and D. Morgan, xe2x80x9cDry Silver Photographic Materialsxe2x80x9d (Handbook of Imaging Materials, Marcel Dekker, Inc. page 48, 1991), etc. These photosentive materials are developed at high temperature of not less than 80xc2x0 C. and are referred to as thermally developable photosensitive materials.
When a printing plate-making photosensitve material is used for color printing, ordinarily, a plurality of films subjected to color separation for each color are employed. These are exposed to each of several printing plates and printing is carried out upon superimposing them. When a plurality of films subjected to color separation for each color are not superimposed in such a manner that each image is identically positioned, a phenomenon termed doubling is caused in resulting prints. Accordingly, in the printing plate-making photosensitive material, it is required that the sizes are identical throughout the development process, that is, the repetition accuracy is critical.
However, the conventional thermally developable photosensitive materials as described above, when developed at high temperatures, have exhibited insufficient size repetition accuracy described above and when employed for color printing, have not been commercially viable. Furthermore, when storing thermally developed samples, the resulting samples have not been commercially viable due to occasional staining and degraded silver tone.
Accordingly, in view of the foregoing, the present invention was accomplished. An object of the present invention is to provide a processing method of a thermally developable photosensitive material which exhibits excellent size repetition accuracy. Another object is to provide a processing method of a thermally developable photosensitive material which results in minimum staining and minimum degradation of silver tone during storage after thermal development processing, and in particular, to provide a processing method of a thermally developable printing plate-making photosensitive material especially suitable for color printing.